Towards a Low-Cost Optical Biosensor System for Biomedical Immunoassay Applications

Keywords

Medical devices, biosensors, immunoassay, optical
system.

Abstract

A novel, low-cost optical measurement system has been
designed for biomedical applications such as
immunoassays. The system comprises a rapid-prototyped
ABS plastic housing, 500 nm LED source, 530 nm UV
filter, and 540 nm silicon photodiode receiver with a
custom-built high gain precision amplifier. The sensor
system has been designed to measure the fluorescence of
different bioliquids in a standard glass test-tube. In
addition, a small disc magnet can be inserted to enhanced
signal-to-noise in liquids containing fluorophore-labelled
magnetic beads. Our preliminary results show that the
baseline optical signal depends weakly on the refractive
index of the liquid and more strongly on its opaqueness.
Removing this baseline signal permits the measurement of
FTIC solutions down to concentrations of about 100
nMol. In addition, the insertion of the magnet was found
to enhance significantly the optical signal in translucent
liquids with low bead concentrations but, interesting, not
in opaque ones. We believe that this low-cost (less than
€150) optical immunoassay sensor has potential
applications such as detecting progesterone and bacteria
levels in milk, water, saliva, urine, and blood.